Belting



Aug. 29, 1950 G. A. SOWERBY ET AL BELTING 2 Sheets-Sheet 1 Filed July25, 1945 a Aw Patented Aug. 29,

UN S TATE S PAT O F FI C E BELTENG George Angus Sowerby, NeWcaStI'eEOnT'YneQ and William Stanley Short, Seaton Bum; Newcastle-'on-T'yne',England, aissi gnors to" George Angus 82 Company Limited;- Newcastle-onTyne,-England Application July ;.194aseiiaI Nb..'6m;025- Iii-GreatBritain August 16; 1'94'4' Belting is frequently manufactured from wovencloth and oftenhas a coating'of rubber ca'lendered on to the drivingface for the purpose of increas ingthe coefficient of" friction.Multi-ply belting is commonly built up of superposed plies of wovenfabric onto which rubber has been calendered, the rubber serving toeffect adhesion between the several plies. It is known to stretchsuchmultiplybelting after the-plies have been stucktogeth'er "and tovulcanise the rubber under heat while-the belting-isso stretched; the,rubber then serving the further purpose of preventing subsequentcontraction ofthe belting. I I

The object of: this invention is to enable belt-- ingf t'o be'manufactured from knitfed textile fab ric. The use of knitted fabric forthis purpose isd'esirable not only because knitting constitutesmorefullyexplai ned the-endsoffa strip-of knitted fabric unlike those ofastrip of woven OYb IaidG'd fabric' can. be joined to form a joint whichistruly' homogeneous: with theremainder of the strip,. which renders theuse of knitted fabric of especial advantage for the manufactureof endless' belting; Woven beltingcan, it is. true, be made truly endless. bya complicated process: of weaving; using: a: warp constituted by a:Single? continuous yarn. This procedure howeveristrelaltively'inconvenient and moreoversufferslfronrthe disadvantagethat the belt can: only be woven toa. definite determined lengthi.Knitting: belting can however be knitted in a. continuous length and cutand joined: to make ahomogeneous belt of anydesiredilengtht Knitted"vfabric; as such, however wouldbe or.

little use for the'man ufacture oi? machinetbel ting o'r-"even' ofconveyor beltingowin'g t'o'its highdegreeof stretch. Thus knitted cottonfabric has an extension of theorder of 50-150% at break; Whereastheexten'sion at break. of. a normal: belt ing is of the order of.15%-.-

In our' patent No; 2 439,586;. issued April T3, 1948-, on an applicationfiled on even date herewith we have-described aimethod' of manufacturinbelting" from: fabric knitted; from rubberised' yarn; which consists. instretching the fabric to a sufiicient extentand subjecting. the rubberto curing} under heat and pressure whilethe: fabric: is maintainedstretched; The knitted fabric", however; has oftentob'e stretchedto'somethi'ng. of the order. of double its length to ensure that therewill be no substantial further extensionot the belting in service and itis not very conven ientto have todo this onthe press;-

2. we ha ve discovered however, that if thef abric is=inipregna=ted;afterknitting, with rubber, either naturaror s ntheuc; ina' wetcondition, i. e: either as latexor as rubber solution; stretclied totherequired extent andfmaintained so stretched until the rubber has driedto-preve ntisubsequent contraction of the fabric.

The present" invention relates" to e; method of manufacturing f-rictiorrsurface belting, and to such belting asan articleof manufacture, suchmethod com-prising the steps of impregnating" a strip of knitted textilefabric with rubber b'y ap plie atiorr thereto of rubber latexor rubbersolu tion; stretchingthe fabric to a sufiicient extent before, during orafter impregnation and main tai'nihg the fabric so st)1*-etehe'd'- untilthe rubber has-dried; The" impregnated fabric will generally besubjected to curing under heat and pressure" although; later explained,is not always essential. "eobjctof the vulcanization under ressureischiefiyto-improve the appearance of" the belt. Only the product" orarticle referred to will be; 'cla'i n'ied in the" present application.This product may be produced by the novel method d'ethe method; deSC'Ii-bed and claimed in our Said Patent 510221489536;-

By' the: expression suflicient extent we meanthat the stretching W-i llbe Sllfficilil'l to prevent any! substantial" rurtherreXtensiQn of thebelting in: sew-ice whether for transmission or conveyor purposes; Thisresult will be achieved when the finiishedi product has? an extension atbreak of about 3-17%, as compared with the-above-quoted figure: forhermi -knitted fabric of- 501'50 It necessary for" the: beltingto have asmall amountoffextensibility to enable: it to operate as a belt; to'ensure: that the spacing of the pu1leys oniwhioh it i'sa-to operateri'snot too criticalgv anditnefig -urerot 11.5 extensionaatbreak i that laiddbwm in the British. Standard Specification for rubberised: canvasbelting as the:- maximum permitted: extensiom For: some purposes; how"-ever; a somewhat larger extension can be toleratedz- The: fabric is.maintained. stretched untilz'the rubber has dried as:- otherwi'se therubber" will dry an-dt lock the yarns: together so as to: render itimpossible (unless: the alternative procedure indicatedbelow isadopte'd) to-irnpart to-the fabricthat stretch in manufacture which isneces-' sary' to eliminate 'any unduetendency to stretch whenz usedi as;belting. Sometimes, how-ever;- it mayr' be advisable to subjectthe:fabric to further stretching: during. curing: on the press; Thiswillthe'd'ried rubber is" effective" not present any difficulty orinconvenience as the fabric is no longer highly extensible.

When the knitted fabric is thoroughly wetted with latex or rubbersolution as described (latex being preferred), and stretched and driedwhile being maintained under stretch, the result will be that theinterconnected loops of which the strip of fabric is formed will beelongated and dried within the knots, by bonding the tightlytied-stitches together, is apparently'the means whereby the knots areprevented from untiein after the stretching force is relieved, Theresult of this is that contraction of the fabric after release of thestretching force is prevented except forany slight contraction which mayoccur in the portions of the yarns between adjacent rows of the rubberplastic, This softening of the rubber enables the fabric to be stretchedto the required extent, and if it is so stretched while the rubber iswarm and maintained stretched until the rubber has cooled, the rubberwill set again and prevent subsequent contraction of the fabric. Thismethod is of course applicable only when uncured 7 rubber is used forthe impregnation, and the fabknots, immediately upon the release of thatforce.

Due to this action of the rubber, curing under heatand pressure is notessential, and indeed we may in suitable cases impregnate the fabricwith vulcanis'ed rubber and so omit the step of curing the belting,relying on the drying of the rubberv alone to prevent subsequentcontraction of the belt. I V V V H The drying of the rubber on thestretched fabric is most conveniently efiected'in an oven, but

we may, in. the case where'latex is employed achieve an equivalentresultgbycoagulating the latex on the fabric, e. g. by introducing theimpregnated fabric into a bath of acid or alcohol, the resultingdeposition of the rubber in and between the yarns being effective toprevent ,con-, traction of the fabric on release of the stretchingforce. 7

Belting according to the invention may be manufactured in single ply orin multi-ply form, bein constituted in the latter case by superposedplies of knitted fabric, laminationbeing effected either before or afterthe impregnation and stretching treatment and the plies being united bycuring the rubber under heat and pressure, with or without theinterposition of adhesive between the plies.

The belting maybe made ends of the strip. This will be done prior to thecuring treatment when this is practised, The joining may be done by handknitting, as described in U. S. Patent No. 2,106,119, dated Januar 18,1938, so as to obtain a joint which is homogeneous with the rest of thebelt. Alternatively the join may be made by chamfering the ends of thebelt to a wedge form and lapping the two wedges under heat and pressure.This method is mainly suitable in the case of multiply belting, as theconstituent plies can 'be cut in stepped formation at each end of thestrip. Where desired, however, the ends of the belt can be joined withstandard fasteners...

As an alternative to stretchin the fabric-and maintaining it stretcheduntil the rubber has dried, we may however impregnate the fabric.

with rubber after knitting and allow the rubber to dry on the fabricwithout stretching, the fabric being afterwards warmed sufficiently torender endlessby joining the ric preferably should be given a finalcuring treatment on the press. Although the rubber may become plasticagain when heated in the press, the pressure applied to the fabricprevents it from contracting and there is no need to stretch the fabricwhile under the press. 7

' One example of the manufacture of belting in accordance with theinvention will be described with reference to the accompanyin drawing,in.

which:-

Fig. 1 is a diagram showing successive stages in the process, and

Fig. 2 is a section on the line IIII in Fig. 1.

Fig, 3 is an enlarged diagrammatic representation of a portion of thefabric showing the loops constituting the knitted fabric beforestretching and treatment with the rubber, and v Fig. l is a similar viewof the fabric after impregnation, stretching and subsequent drying.

A strip ll] of knitted fabric, knitted on a knitting machine from cottonfreefrom rubber, and of greater width and thickness than the final beltrequired, is dropped into a bath H of latex or rubber solution. Whenthoroughly wetted it is withdrawn by a pair of spiked rollers 12. Fig. I

being purely diagrammatic the spikes on rollers [2 are not shown.Thefab-ric then passes toa second pair of spiked rollers l3 rotating, ata higher speed than the rollers l2 thus imparting to the fabric atregion A the necessary degree of stretch. The stretched fabric is takenaway. from rollers [3 by a third pair of spiked rollers.

I4 which rotate at the same speed as rollers l3. Between rollers l3 andI4 the fabric passes through a drying oven l5. The rubber is thus driedon the fabric while it is maintained stretched. r

From rollers 14 the fabric is taken to a heated ress l6 havin dieswhich, when closed, define a mould cavity I! of the section of thefinished beltrequired.

The fabric is cured in the press bit by bit, the press remaining closedfor the required vulcanising period, which may befrom 5 to 20. minutesaccording to the temperature and rubber composition which have beenselected.

The cured fabric is-then'cut to length quired, and joined to form abelt. While the fabric has been shown passing directly from the rollersM to the presslfi, it will be understood that it may be necessary inpractice to use'a discontinuous process, laying thefabric aside afterrubberising, stretching and drying, and appl i the curing treatmentsubsequently.

Theoperation of the process and the formation of theresulting productwill be indicated further by reference toFigures 3 and 4. In theoriginalknitted state the loops of the fabric, such as [8, I9, 20, assume theforms of naturally easy' the. stitches straighten to form the elongatedloops shown in Fig. 4, with the crossing stitches at the intersectionsof the loops drawn into tight knots, a is indicated at 21 22 Theoukrsurfaces of the stitches are coated with rubber, as is indicated at 23,after the drying is completed, the relatively small amount of rubberwithin the knots, indicated at 24, coating the adjacent surfaces ofcrossing stitches and extending continuously therebetween to bond thesesurfaces together, to prevent the untieing of the knots. The interiorsof the loops will, to a considerable extent, be free of rubber, afterthe drying is completed, but if the belt is subsequently cured underheat and pressure these voids will naturally become much smaller, inaccordance with the pressure used.

While the invention has been described with reference to its applicationto fabric knitted from yarn free from rubber, it may nevertheless alsobe applied to fabric knitted from rubberised yarn while in a wet orlubricated condition, the knitted fabric bein thereafter impregnatedwith wet rubber, stretched and held stretched until the rubber hasdried. We prefer to knit the fabric from rubberized yarn because of theimproved friction properties of the belts made therefrom in comparisonwith belts knitted from unrubberized textile yarn, in which the onlyrubber present is that applied for the purpose of holding the beltagainst contraction from its stretched length, it being noted that therubber of the rubberized yarn, which is in effect an integral portion ofthe yarn itself, plays no part in preventing the fabric from stretchingor contracting. It Will also be observed that when a belt made from thefabric knitted of rubberized yarn is subsequently cured under heat andpressure the voids within the loops of the knitted fabric will becomesmaller than is the case when a belt made from the unrubberized knittedfabric is cured under equal pressure, because of the fact that there ismuch more rubber in the article in the first case, to flow under heatand pressure and therefore to some extent to fill the voids. The fabriccan be knitted from any desired textile yarn, e. g. cotton or flax.

What we claim as our invention and desire to secure by Letters Patentis:

1. A friction surface belt comprising a strip of knitted fabric formedof elongated interconnected loops stretched in the lengthwise direction6 of the strip and tied together into tight knots at theirintersections, substantially all of the surfaces of the stitchescomprisin the same being coated with rubber, with the adjacent surfacesof crossing stitches Within the knots being bonded together by rubber,the said belt having substantially no tendency to contract and having anextension at break of about 3 to 17 per cent.

2. A friction surface belt comprising a strip of knitted fabric formedof elongated interconnected loops stretched in the lengthwise directionof the strip and tied together into tight knots at their intersections,substantially all of the surfaces of the stitches comprising the samebeing coated with rubber, with the adjacent of crossing stitches Withinthe knots being bonded together by rubber, the said belt havingsubstantially no tendency to contract and having an extension at breakof about 3 to 17 per cent, the belt having a friction surface of rubberon both faces thereof, all of the rubber in the belt being in a curedcondition.

3. A friction surface belt comprising a strip of fabric knitted fromrubberized textile yarn, formed of elongated interconnected loopsstretched in the lengthwise direction of the strip and tied togetherinto tight knots at their inersections, substantially all of thesurfaces of the stitches comprising the same being coated with rubber,with the adjacent surfaces of crossing stitches within the knots beingbonded together by rubber, the said belt having substantiall no tendencyto contract and having an extension at break of about 3 to 17 per cent.

GEORGE ANGUS SOWERBY. WILLIAM STANLEY SHORT,

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,697,236 Gingas Jan. 1, 19291,929,839 Dawson Oct. 10, 1933 2,004,110 Head June 11, 1935 2,005,407Abrahamsen et a1. June 18, 1935 2,106,119 Krasselt Jan. 18, 1938

